Speaking for the first time since 49ers coach Jim Harbaugh confirmed Colin Kaepernick's "hot hand" would start at quarterback Sunday at St. Louis, the demoted Smith appeared agitated over once again losing a job that's repeatedly been swiped from his grasp since he was drafted first overall in 2005.

"I feel the only thing I did to lose my job was get a concussion," said Smith, who sustained that brain trauma Nov. 11 during the second quarter of a 24-24 tie with the Rams.

Smith did not, however, blast Harbaugh's communication methods.

"We sat down and talked. It wasn't a one-sentence thing," Smith said. "He explained where he was coming from, felt it was a difficult situation but wanted to go in this direction."

Did Smith try to talk Harbaugh out of starting Kaepernick for a third straight game?

"No, I mean at this point, what's talk going to do?" Smith responded. "I felt he made up his mind. He's not a guy who didn't put thought into it already."

In his last full outing, Smith completed 18 of 19 passes in a 24-3 win at Arizona, earning him a first-career NFC Offensive Player of the Week award. Dating back to halftime of an Oct. 18 win over Seattle, Smith is 35 of 38 for 385 yards with five touchdowns and one interception.

"It's tough. You state your case with your play, and I feel I've done that," said Smith, who leads the NFL with a 70.0 completion percentage and ranks fifth with a 104.1 passer rating.

Smith said he found out about this week's benching "a couple days ago" from Harbaugh, who announced it to the team after Wednesday morning's walk-through practice. Smith holds "no resentment" toward Harbaugh, saying that such decisions are what Harbaugh "gets paid to do."

Kaepernick's first career starts have produced big-stage wins over the Chicago Bears and New Orleans Saints. Offensive coordinator Greg Roman praised Kaepernick's "natural progress" and a "more efficient" throwing motion.

Smith's next step is to prepare for his next chance on the field, at which time he plans to "make the most of my next opportunity."

That could come in relief of Kaepernick, or perhaps next season on another team. Smith's 2013 base salary of $7.5 million is guaranteed only if he's on the 49ers' roster on April 1, according to CSN Bay Area's Matt Maiocco.

Of all his ups and downs -- and through the coaching and coordinator changes he's endured -- Smith is particularly stung by the timing of this benching.

"It's such a great team, a great group of guys in the locker room, and something special is going on here," Smith added. "It's a tough pill to swallow."

Across the locker room, defensive tackle Ray McDonald sat at his locker and put in perspective the NFL's harsh reality.

"It does suck to kinda lose your job to injury, but that happens in the NFL," McDonald said. "Guys move on, they have mouths to feed and want to win championships. You've got to put it in the back of your mind."

Smith harbored no regrets about informing team officials about the blurred vision he experienced that signaled his Nov. 11 concussion.

"No, I'm not looking back on that," Smith added.

Former 49er Bill Romanowski told 95.7 The Game that Smith's cautious approach opened the door for Kaepernick. Said Romanowski: "If Alex Smith would've played through the ding, the concussion, like a lot of guys still do ... Careful in the NFL means losing your job. And that's what this did for him."

Smith endorsed the league's recent emphasis on reporting concussions and called it "a good thing." He did note that it is a "good question" if others will hesitate to report their symptoms in fear of losing their job to their injury replacement.

"It stings the most because I really feel like there's something special going on here," Smith added. "You sacrifice and you invest so much time. Like I said, I really feel like I hadn't done anything but get a concussion to really facilitate this. I feel like I was playing good football."

A week ago, Smith sounded resigned that his benching could be forthcoming, and a few hours later, Sports Illustrated's Jim Trotter correctly reported that Kaepernick would start Sunday's game at New Orleans.

While Smith's status remained in limbo, another clue emerged Saturday that Smith wouldn't be reclaiming his job, and it came in the form of a tweet from Smith's wife.

Elizabeth Smith tweeted: "I am beyond thankful to walk through life with an amazing man by my side. He is the perfect example for our sons and my best friend. No matter what life throws his way, he has the utmost respect, honesty and integrity. Something a lot of people lack these days:(#thankful."